1. Field of the Invention
The present invention relates to a center mechanism vertically moving an upper ring with respect to a lower ring of a tire press and a tire press using the same.
2. Description of the Related Art
In the past, green tires molded by a molding machine are stored under the environment of room temperature in a rack of a predetermined storage places, afterward, are taken out of the rack on the basis of a production plan, and are carried into a press. In this case, for example, in a bladder type press, the green tire is charged into a mold by clamping a mold, and afterward, a pressure medium of high temperature and high pressure is supplied into a bladder inserted into a tire hole whereby the bladder is extended into close contact with the inner wall surface of a tire. Then, the inner wall surface of a tire is pressed in a direction of a mold while heating the inner wall surface of a tire though the bladder to thereby form a tire groove of a mold in a tread part of the green tire. Further, the green tire is heated from outside and inside by a mold heated and a bladder in contact with the pressure medium of high temperature to rise a temperature of the green tire to a press starting temperature (100xc2x0 C. to 120xc2x0 C. or higher) quickly whereby press molding is completed in a short period of time.
In the above-described prior art, the outside and the inside of the green tire are heated by the mold and the bladder so as to complete the press molding in a short period of time. However, since the green tire is mainly constituted from rubber having a low heat conductivity, even if the surface side of the green tire should be risen in temperature in a short period of time, a rise in temperature of the internal side is delayed, and particularly, the delay in rise of temperature of the internal center in a tread wall-thickness part having a large thickness or a bead part is conspicuous. Accordingly, even in a case where pressing of the surface portion of the green tire is completed, it is necessary to continue press molding till pressing of the inside in which a rise in temperature to a press temperature is delayed, thus posing a problem that press molding cannot be completed in a short period of time sufficiently.
It is therefore an object of the present invention to provide a center mechanism of a tire press capable of completing press molding in a short period of time.
For achieving the above-described object, the present invention provides a center mechanism of a tire press comprising: a lower ring, an upper ring, a center post, said center post being extended vertically movably through a center part of said lower ring to vertically move said upper ring with respect to said lower ring, heating means, and moving means capable of moving said heating means to a suitable position independently of vertical movement of said center post, wherein said heating means may be arranged, when a tire is held between said lower ring and said upper ring, in the position capable of heating the inside of the tire.
According to the above-described constitution, the heating means is moved so as to principally apply the heat to the wall-thickness part of the green tire whereby the wall-thickness part can be risen in temperature rapidly. Thereby, the whole green tire can be risen in temperature to a press temperature in a shorter period of time than a case where a heating medium such as high temperature vapor is supplied to the inner peripheral side of a tire of the green tire, and the whole green tire is heated with uniform heat by the heating medium alone. Accordingly, press molding can be completed in a short period of time. Further, if a great heat is released from said heating means, press molding can be carried out with that heat, thus being unnecessary to supply a high temperature heating medium. As a consequence, costs required for a device for supplying a heating medium can be reduced.
The center mechanism of the tire press according to the present invention comprises a tubular member movably fitted over the center post, and the heating means is mounted on the tubular member. The heating means can be a heater provided to be wound around a partial region of the tubular member. Further, the moving means may comprise a first driving mechanism for vertically moving the tubular member.
According to the above-described constitution, the heater can be mounted easily on the tubular member, and by the simple constitution of the first driving means, the tubular member is vertically moved to a suitable height position to thereby cause the heater to come close to the wall-thickness part of the green tire to principally heat the wall-thickness part.
In the center mechanism of the tire press according to the present invention, the moving means further comprises a second driving mechanism for rotating the tubular member about the center post.
According to the above-described constitution, since heat generating means is turned about the center post by rotation of the tubular member, even if the heat generating member is provide in a part in the peripheral direction of a mounting region or heat-generated in a peripherally uneven state, the heat can be applied uniformly to the whole green tire in the peripheral direction.
Further, in the center mechanism of the tire press according to the present invention, the heating means can be a directional lamp set so as to emit light in a predetermined direction to apply the heat.
Further, the present invention provides a tire press comprising a mold, mold heating means for heating the mold, in which a green tire is mounted within the mold by clamping the mold when subjected to press-processing, a bladder, means for supplying a heating medium into the bladder, and the center mechanism described above. When a green tire is press-processed, the bladder is placed in close contact with the inner wall surface of the green tire.
According to the above-described constitution, added to means for supplying a heating medium such as high temperature vapor to the inner peripheral side of the green tire and heating the whole green tire with uniform heat by the heating medium is heating means for principally applying the heat to a portion that is hard to be risen in temperature such as the wall-thickness part, whereby the whole green tire can be risen in temperature to a pressing temperature in a short period of time.
The tire press according to the present invention may further comprise a high frequency power source, and a heating coil supplied with power from the high frequency power source.
According to the above-described constitution, it is possible to further increase the heat applied to a portion that is hard to be risen in temperature such as a wall-thickness part, and is further possible to rise a temperature of the whole green tire to a pressing temperature in a short period of time.